Happy birthday, lava lamp

The BBC has a story on the 50th anniversary of the famous lava lamp. It is called Lava lamp creators mark 50 years of 1960s icon.The 50 refers to the 1963 date of setting up the original company.

I enjoyed it, and am providing links here to the two key patents.

In 1964 Crestworth Limited applied for what was published as the patent called Display device. Below is the main drawing.

However, there were four problems with this first model. This was explained in a second patent, filed in 1967 by Edward Walker, the former RAF officer who thought up the idea in the first place.

This was also called Display device. The first problem was that as it took a long time for the device to become ready when switched on, "It has now been found that some viewers may become impatient during the preliminary heating up period." The second was that if left on for a long time, overheating caused the globules to break up into "unattractive tiny droplets". The third was that the apparatus could freeze and therefore break in cold periods. The fourth was that draughts could cause problems, requiring careful positioning of the lamp.

All these problems were solved by adding something to the fluid. A "water-miscible liquid.".

Anti-freeze, in other words.